Consul — service discovery and health checking

How does service A find out where service B is running? Hardcoded IP? Load balancer? Consul from HashiCorp offers an elegant solution: service discovery with health checking, a KV store, and a DNS interface — all in one.

Registration and health checks¶

{
  "service": {
    "name": "user-api",
    "port": 8080,
    "tags": ["v2", "production"],
    "check": {
      "http": "http://localhost:8080/health",
      "interval": "10s"
    }
  }
}

DNS interface: user-api.service.consul returns the IPs of healthy instances. Any application that can use DNS benefits from this without any integration effort.

Consul vs. etcd vs. ZooKeeper¶

etcd: pure KV, no service discovery. ZooKeeper: robust, but complex. Consul: the most complete solution — SD + health checks + KV + DNS.

Service discovery is a prerequisite for microservices¶

Consul is currently the best choice. Deployment takes a day; operations are trouble-free.